Climate change, habitat loss and toxic chemicals are among many factors that threaten the health of our environment and directly or indirectly contribute to biodiversity loss.  Physiological constraints and/or requirements shape individuals’ behavioral and life history characteristics and provide linkages with population processes and conservation policies.  The study of energy flows, sources, and sinks, across levels of biological organization provides useful insights into ecological organization and function.  Energetic approaches allow scientists to rank the quality of habitats or to ask how individual time and energy budgets translate into population changes.  For the restoration of Sacramento perch (Archoplites interruptus), a threatened endemic Californian sunfish, we measured its physiological tolerance and metabolic responses to water physical-chemical parameters.  We also monitored water quality of the watersheds in which they reside.  The data are used in a dynamic bioenergetics model, which incorporates an environmental subunit that can influence where energy within the organisms is allocated.  Thus, we can begin to predict environment effects on the growth of this species as well as its potential fecundity and population estimates.  These results are essential in the selection of Sacramento perch restoration sites and in predicting population-level effects of global events, such as climate change.